Search results for " systematic"
showing 10 items of 6683 documents
Redescription of Chiropturopoda nidiphila Wiśniewski & Hirschmann (Acari: Uropodina) from a woodpecker’s tree holes, including all development stages…
2021
All development stages of Chiropturopoda nidiphila Wiśniewski & Hirschmann, 1983 are described, which has previously been known only from the deutonymph stage. The species is closely associated with tree holes excavated by woodpeckers. Chiropturopoda nidiphila was redescribed and the genus diagnosis was completed. The description of the species morphology is based largely on scanning (SEM) electronograms. Diagnoses differentiating all of the known species of the genus Chiropturopoda are provided, including their developmental stages.
Ecologists overestimate the importance of predictor variables in model averaging: a plea for cautious interpretations.
2014
Abstract: Information-theory procedures are powerful tools for multimodel inference and are now standard methods in ecology. When performing model averaging on a given set of models, the importance of a predictor variable is commonly estimated by summing the weights of models where the variable appears, the so-called sum of weights (SW). However, SWs have received little methodological attention and are frequently misinterpreted. We assessed the reliability of SW by performing model selection and averaging on simulated data sets including variables strongly and weakly correlated to the response variable and a variable unrelated to the response. Our aim was to investigate how useful SWs are …
Variation in the Sizes of Chthamalid Barnacle Post-Settlement Cyprids on European Shores
2001
As part of a wider study on the settlement and recruitment of Chthamalus spp. in Europe, this study investigated whether chthamalid cyprids can be separated by length on a European scale. Variation in cyprid length with latitude and temporal variation at selected localities were also examined. The lengths of cyprids collected between 1996-1999 on nine rocky shores in Europe are reported. Elminius modestus cyprids were found only at Roscoff, NW France and could be distinguished due to their Carapace shape and length. They showed a unimodal length distribution, measuring between 450 and 625 mum, with no variation in length between the two sampling dates (1997 and 1998). Based on carapace shap…
A new species within the Centaurea busambarensis complex (Asteraceae, Cardueae) from Sicily
2022
The Centaurea busambarensis group is made up by eight species endemic to Sicily. We statistically evaluated a population found on the Nebrodi Mountain (NE Sicily) to verify if the observed morphological differences with the already known taxa justified the description of a new one. It resulted in being sufficiently distinct to deserve recognition at the species level. Centaurea valdemonensis, a new species endemic to Sicily is described and illustrated here. It is confined to the Nebrodi Mountains (NE Sicily). The distinction of this taxon from the others belonging to the C. busambarensis complex has been supported with the aid of statistical analyses on morphological characters. The differ…
No phylogeographic structure in the circumpolar snowy owl (Bubo scandiacus)
2008
The snowy owl (Bubo scandiacus) is a nomadic species with a circumpolar distribution. It has recently declined in the western Palearctic and may thus be worthy of special consideration for conservation. We investigated genetic structure in three well separated geographic regions within the snowy owls’ breeding range. We sequenced two mitochondrial genes; the control region and cytochrome b, and two Z-chromosome introns; VLDLR-9 and BRM-15. We found no phylogeographic structure among the sampled regions, indicating high levels of gene flow in the recent past and possibly still today. Intra-population diversity did not vary between regions for the control region, but for Cyt b, North American…
Phylogeography of a Palaearctic sedentary passerine, the willow tit (Parus montanus)
2001
We analysed variation of the mitochondrial control region from willow tits through its Palaearctic distribution range. Although we found high amount of genetic variation (π=1.114%), there was almost no differentiation between subspecies or geographical localities. This may be because of a combination of several ecological and genetic factors, including a relatively homogenic habitat through the distribution range, lack of geographical barriers, high gene flow and a large long-term effective population size. On the contrary, in the songar tit, which is sometimes considered to be conspecific with the willow tit, the mitochondrial lineages seem to correlate with the geographical locality and a…
Environmental features of deep-sea habitats linked to the genetic population structure of a crustacean species in the Mediterranean Sea
2009
The deep-sea habitat, from 200 to 2000 m depth, has long been thought as an ecosystem where biotic and abiotic factors vary very little and consequently species are not disturbed by processes and phenomena which could promote fast evolutionary mechanisms. Unfortunately, biological information relating to deep water is limited, especially regarding the population genetics of species inhabiting the Mediterranean Sea, and general patterns cannot be inferred. In this study we report data on the population genetic structure of Aristeus antennatus, a deep-sea decapod crustacean species which has been widely studied due to its important economic value. We surveyed and examined the variation in a 3…
Conceptualizing ecosystem tipping points within a physiological framework
2017
Connecting the nonlinear and often counterintuitive physiological effects of multiple environmental drivers to the emergent impacts on ecosystems is a fundamental challenge. Unfortunately, the disconnect between the way “stressors” (e.g., warming) is considered in organismal (physiological) and ecological (community) contexts continues to hamper progress. Environmental drivers typically elicit biphasic physiological responses, where performance declines at levels above and below some optimum. It is also well understood that species exhibit highly variable response surfaces to these changes so that the optimum level of any environmental driver can vary among interacting species. Thus, specie…
The role of in situ species diversification for the evolution of high vascular plant species diversity in the European Alps—A review and interpretati…
2017
Abstract By harbouring ca. 3500 native vascular plant species in an area of ca. 170 000 km2, the European Alps represent a region of very high species diversity. Using the most recently published flora of the area and phylogenetic literature, I here review which proportion of the endemic flora of the Alps is the result of in situ diversification, i.e., of diversification in the area and (largely) restricted to the area. There exist only very few and mostly species-poor species diversifications in the Alps, accounting for ca. 1.2% of the native and for ca. 9% of the endemic flora of the Alps. In contrast to this, ca. 33% of the endemic species of the Alps belong to lineages widespread in the…
Lymphatic vessels of the dura mater: a new discovery?
2015
Aspelund et al. discover the presence of a lymphatic vessel network in the dura mater of the mouse brain and show that these dural lymphatic vessels are important for the clearance of macromolecules from the brain.